sshd: use drop-in for basic sshd configuration

This saves us from having to rebase on every upstream config change.

roles/sshd/tasks/main.yml

 - name: Install openssh
   pacman: name=openssh state=present
 
-- name: Configure sshd
-  template: src=sshd_config.j2 dest=/etc/ssh/sshd_config owner=root group=root mode=0644 validate='/usr/sbin/sshd -t -f %s'
+- name: Configure sshd via drop-in
+  template: src=sshd_config.j2 dest=/etc/ssh/sshd_config.d/override.conf owner=root group=root mode=0644 validate='/usr/sbin/sshd -t -f %s'
   notify:
     - Restart sshd
 

roles/sshd/templates/sshd_config.j2

-# Include drop-in configurations
-Include /etc/ssh/sshd_config.d/*.conf
-
-# This is the sshd server system-wide configuration file.  See
-# sshd_config(5) for more information.
-
-# This sshd was compiled with PATH=/usr/local/sbin:/usr/local/bin:/usr/bin
-
-# The strategy used for options in the default sshd_config shipped with
-# OpenSSH is to specify options with their default value where
-# possible, but leave them commented.  Uncommented options override the
-# default value.
-
 Port {{ ansible_port | default(22) }}
-#AddressFamily any
-#ListenAddress 0.0.0.0
-#ListenAddress ::
-
-#HostKey /etc/ssh/ssh_host_rsa_key
-#HostKey /etc/ssh/ssh_host_ecdsa_key
-#HostKey /etc/ssh/ssh_host_ed25519_key
-
-# Ciphers and keying
-#RekeyLimit default none
-
-# Logging
-#SyslogFacility AUTH
 LogLevel VERBOSE
-
-# Authentication:
-
-#LoginGraceTime 2m
-#PermitRootLogin prohibit-password
-#StrictModes yes
-#MaxAuthTries 6
-#MaxSessions 10
-
-#PubkeyAuthentication yes
-
-# The default is to check both .ssh/authorized_keys and .ssh/authorized_keys2
-# but this is overridden so installations will only check .ssh/authorized_keys
-AuthorizedKeysFile	.ssh/authorized_keys
-
-#AuthorizedPrincipalsFile none
-
-#AuthorizedKeysCommand none
-#AuthorizedKeysCommandUser nobody
-
-# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
-#HostbasedAuthentication no
-# Change to yes if you don't trust ~/.ssh/known_hosts for
-# HostbasedAuthentication
-#IgnoreUserKnownHosts no
-# Don't read the user's ~/.rhosts and ~/.shosts files
-#IgnoreRhosts yes
-
-# To disable tunneled clear text passwords, change to no here!
 PasswordAuthentication no
-#PermitEmptyPasswords no
-
-# Change to no to disable s/key passwords
-#KbdInteractiveAuthentication yes
-
-# Kerberos options
-#KerberosAuthentication no
-#KerberosOrLocalPasswd yes
-#KerberosTicketCleanup yes
-#KerberosGetAFSToken no
-
-# GSSAPI options
-#GSSAPIAuthentication no
-#GSSAPICleanupCredentials yes
 
-# Set this to 'yes' to enable PAM authentication, account processing,
-# and session processing. If this is enabled, PAM authentication will
-# be allowed through the KbdInteractiveAuthentication and
-# PasswordAuthentication.  Depending on your PAM configuration,
-# PAM authentication via KbdInteractiveAuthentication may bypass
-# the setting of "PermitRootLogin prohibit-password".
-# If you just want the PAM account and session checks to run without
-# PAM authentication, then enable this but set PasswordAuthentication
-# and KbdInteractiveAuthentication to 'no'.
-#UsePAM no
-
-{% if 'buildservers' in group_names %}
-#AllowAgentForwarding yes
-#AllowTcpForwarding yes
-{% else %}
+{% if 'buildservers' not in group_names %}
 AllowAgentForwarding no
 AllowTcpForwarding no
+{% else %}
+Match User root
+	AllowAgentForwarding no
+	AllowTcpForwarding no
 {% endif %}
-#GatewayPorts no
-#X11Forwarding no
-#X11DisplayOffset 10
-#X11UseLocalhost yes
-#PermitTTY yes
-#PrintMotd yes
-#PrintLastLog yes
-#TCPKeepAlive yes
-#PermitUserEnvironment no
-#Compression delayed
-#ClientAliveInterval 0
-#ClientAliveCountMax 3
-#UseDNS no
-#PidFile /run/sshd.pid
-#MaxStartups 10:30:100
-#PermitTunnel no
-#ChrootDirectory none
-#VersionAddendum none
-
-# no default banner path
-#Banner none
-
-# override default of no subsystems
-Subsystem	sftp	/usr/lib/ssh/sftp-server
 
 # unlink forwarded sockets; for gpg agent forwarding
 StreamLocalBindUnlink yes
-
-# Example of overriding settings on a per-user basis
-#Match User anoncvs
-#	X11Forwarding no
-#	AllowTcpForwarding no
-#	PermitTTY no
-#	ForceCommand cvs server
-
-{% if 'buildservers' in group_names %}
-Match User root
-        X11Forwarding no
-        AllowAgentForwarding no
-        AllowTcpForwarding no
-{% endif %}